Analysis of Diffuse Reflection of Laser Range Finder
Usually, in order to reduce the error, those laser range finders will have a reflective surface on the side of the measured end to reduce the error caused by diffuse reflection. How do those telescope-type laser range finders used by snipers overcome this problem? The working principle of the laser rangefinder is similar to that of sonar, but will the signal receiving the reflected light be easily interfered by other wavelengths and intensities of light in the environment?
The detection device of the laser rangefinder (pulse type) generally uses an avalanche photodiode, which is only sensitive to light of a specific wavelength. If the wavelength matches, even a very small light intensity can be detected by it. If the wavelength does not match, even if the light intensity is large , also cannot be detected. The laser just has the characteristics of good monochromaticity, and the commonly used wavelength is 905nm. Therefore, the signal receiving the reflected light is not easily interfered by other wavelengths and intensities of light in the environment.
There are two commonly used schemes for laser ranging: pulse method and phase method.
The phase method measures the distance by measuring the phase deviation of the returned wave. This needs to cooperate with the target, which is what you call a reflective surface on the measured end. In this case, the transmission power of the range finder is small.
The telescope-type laser range finder used by snipers generally uses the pulse method, that is, sends out a pulse, starts timing, and stops timing after receiving the reflected pulse to achieve the purpose of distance measurement. In this case, when there is no cooperative target, the loss of light energy due to diffuse reflection is very serious, but generally it does not affect the measurement. The reason is as mentioned above. Generally, the transmit power of the range finder will be increased to make a certain compensation.
